[AMRadio] AM Transmitter Advice??

Bob Bruhns bbruhns at erols.com
Sat Feb 18 20:00:13 EST 2006

My memory is getting old, and it was always a little
flakey, but I really seem to remember that there was,
at least at one time, an FCC spec on the time constant
of the plate meters in amateur transmitters.

I did a search, but all I could find was this hint:

Drake L-4B Linear Amplifier
"Plate Current Meter time constant is consistent wit

  Bacon, WA3WDR

----- Original Message ----- 
From: "Jim Wilhite" <w5jo at brightok.net>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Saturday, February 18, 2006 7:28 PM
Subject: Re: [AMRadio] AM Transmitter Advice??

> Bacon, not trying to be contrite, but where in the
old rules did the .25
> second time constant appear?  I have a copy of the
old rules and don't see
> it.  It says only that "have the means".
> 73  Jim
> W5JO
>   At that time, plate power input to an AM
> > transmitter was measured by the reaings of DC
> > with approximately 0.25 second time constant.  That
> > time constant would make the meters read average
> > voltage and current, which smoothed out SSB and
> > controlled carrier signals.  But on plate-modulated
> > it did not read true power during modulation,
> > it was looking at average voltage and average
> > separately, while in AM the voltage and current are
> > separate, but they increase and decrease together,
> > resulting in higher power input during modulation.
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